Application case of intelligent photovoltaic combiner box in 10MW photovoltaic power generation project in Turpan, Xinjiang

Customer Pain Points and Needs:
1. Customer Pain Points
Extreme Environmental Impacts: Frequent sandstorms and large temperature swings between day and night in the Turpan desert region damage photovoltaic modules, mounting systems, and other equipment, impacting equipment lifespan and power generation efficiency.
Unstable Power Generation Efficiency: Dust easily covers the surface of photovoltaic modules, reducing power generation efficiency. Furthermore, the angle of sunlight varies significantly between seasons, and failure to adjust the photovoltaic array angle in a timely manner can also affect power generation.
Grid Connection and Energy Consumption Challenges: Achieving convenient grid connection, avoiding the additional costs of booster station construction, and ensuring flexible power generation and mitigating the risk of curtailment and power rationing present challenges.
2. Customer Needs
High-quality photovoltaic combiner boxes are required to provide effective protection for photovoltaic modules and improve equipment reliability and stability.
The combiner boxes must withstand extreme environments such as sandstorms and large temperature swings.
Improve the power generation efficiency of photovoltaic modules and reduce the impact of factors such as dust on power generation.
Ensure convenient grid connection, ensure flexible power generation, and enhance the project's economic viability.
Photovoltaic panels are connected in series in groups of 20. Solution Design: Customized 20-input, 1-output Smart PV Combiner Box Service
1. Calculate the Required Rated Voltage and Current of the Combiner Box

Rated Voltage: 20V * (550W/12A) ≈ 917V
Rated Output Current: 20 * 12A ≈ 240A

2. Core PV Combiner Box Configuration

Model: LQT-20/1M1
Quantity of Combiner Boxes: 46
Wiring Method: 20-input or 19-input, 1-output

Core Configuration
PV-Specific Fuse: Each input is equipped with a 15A/1000V DC PV fuse (designed for 1.25 times the string short-circuit current, or 12 * 1.25). This fast-blow fuse has a breaking capacity of 33kA and provides overcurrent protection. If a fault occurs in a PV string, it will quickly open, preventing the fault from spreading to other strings. The fuse holder is made of high-temperature and aging-resistant materials to ensure long-term stable operation.

DC Molded Case Circuit Breaker: This DC molded case circuit breaker features a total output of 250A/1000V DC (maximum output current calculated as 20*12A = 240A). It provides switching circuits, short-circuit and overload protection, and a breaking capacity of 20kA, enabling circuit opening and closing according to system requirements.

T2 Surge Protector: This device features a 20kA/40kA 1000V DC DC lightning protection module. It utilizes a multi-stage lightning protection design with a response time of ≤25ns. When struck by lightning or a surge, it rapidly discharges the surge current to the ground, protecting the combiner box and subsequent equipment from damage. The lightning protection module also features a degradation indicator, facilitating timely replacement.

Monitoring Module: This module integrates data acquisition and transmission capabilities, utilizing an industrial-grade microcontroller as its core controller. It features an RS485 communication interface and supports the Modbus-RTU protocol, enabling real-time upload of collected current, voltage, temperature, and other data to the customer's backend monitoring system. The monitoring unit operates within a temperature range of -40°C to 70°C, ensuring stable operation in extreme temperatures.

2. Installation and Optimized Design
Installation Requirements:
Installation Location: Select a high, well-ventilated, unobstructed location away from flammable, explosive materials, and sources of corrosive gases. The bottom of the combiner box must be at least 0.5m above the ground and secured with a bracket. The bracket must be sturdy and reliable, capable of withstanding the weight of the combiner box and external forces such as wind loads.
Wiring Specifications: Input and output cables should use dedicated photovoltaic DC cables. The cable cross-section should be selected based on the current to ensure the required ampacity. Cables must be properly sealed when connected to the combiner box to prevent ingress of dust and rain. Terminals must be securely fastened to prevent loose connections that could cause poor contact.
Grounding Connection: The protective grounding terminal of the combiner box must be securely connected to the project grounding grid. The grounding wire should be copper cable with a cross-sectional area of ​​at least 16mm². The connection points must be treated with anti-corrosion treatment. Optimized Design:
Dust Protection: A removable filter is added to the outside of the dust screen on the heat dissipation vents. Regular cleaning of the filter reduces dust intrusion into the box. The door seal is made of water-swellable material, further enhancing the box's seal and preventing dust from entering through the door gap.
Optimized Maintenance: An internal lighting device is installed in the combiner box, automatically illuminating when the door is opened, facilitating maintenance work in dimly lit environments. The components are strategically arranged, with ample operating space reserved for easy installation, commissioning, and component replacement. External signage indicates the corresponding component string number, electrical parameters, and other information for the input branch, facilitating maintenance and management.

Project Highlights:

Cost Optimization: Project costs are reduced through compact land layout, optimal energy storage system configuration, and the elimination of a booster station. A monitoring module connects data to the network, reducing maintenance costs. Strong Environmental Adaptability: A series of protective measures, such as wind-proof ballasts for modules, hydrophobic nanomaterial coatings, and flexible bracket connection designs, have been implemented to address the extreme conditions of the Turpan desert region, ensuring stable project operation.
Easy Grid Connection and Consumption: Directly connected to the local 35kV distribution network, 80% of the power is supplied directly to surrounding industrial parks, mitigating the risk of curtailed solar power and power rationing, and improving project economics.
Fully Leveraging Policy: Benefiting from Xinjiang's "registration-as-construction" policy for distributed photovoltaic projects, this streamlines the approval process and expedites project progress.

Project Achievements

Significant Economic Benefits: The project has a total investment of approximately 43 million yuan, generating an average annual power generation revenue of 7.56 million yuan, a payback period of 7.5 years, and an IRR (25-year cycle) of 9.2%, exceeding the industry benchmark by 8%, demonstrating excellent profitability.
Stable Power Generation Efficiency: Annual power generation is approximately 18 million kWh, with an annual equivalent utilization of 1,800 hours. Through the application of various technologies and equipment, the impact of factors such as sandstorms on power generation efficiency has been effectively reduced. Good Environmental Benefits: As a clean energy project, photovoltaic power generation can reduce reliance on traditional fossil fuels, lower carbon emissions, and play a positive role in protecting the local ecological environment.
Outstanding Social Benefits: The project's construction and operation have created a number of local employment opportunities, promoted the development of the local new energy industry, and provided a stable

power supply to surrounding industrial parks, ensuring the smooth operation of industrial production.
Mature Technology: The project has successfully implemented various advanced technologies and equipment, such as the smart photovoltaic combiner box, providing valuable experience for photovoltaic projects in similar regions.